A successor communication scheme to W-CDMA (Wideband Code Division Multiple Access) and HSPA (High Speed Packet Access), that is, Evolved UTRA and UTRAN (also referred to as LTE (Long Term Evolution) or Super 3G) is being discussed in W-CDMA standardization group 3GPP (3rd Generation Partnership Project). In the E-UTRA, for example, OFDMA (Orthogonal Frequency Division Multiple Access) and SC-FDMA (Single-Carrier Frequency Division Multiple Access) are utilized for downlink and uplink, respectively.
The OFDMA is a multicarrier transmission scheme where a frequency band is divided into multiple narrower frequency bands (subcarriers) and data is transmitted in the individual subcarriers. The OFDMA achieves fast transmission by arranging the subcarriers in the frequency band densely while partially overlapping the subcarriers without interfering with each other, resulting in higher frequency utilization efficiency. In addition, the OFDMA can remove multipath interference in multiple streams within a guard interval section. Therefore, the OFDMA has high affinity with MIMO multiplexing. In addition, link capacity can be increased by frequency scheduling. Also, in the OFDMA, since soft handover combining can be performed between cells, reception quality can be improved. Especially, the soft handover combining is applied to MBSFN (Multicast/Broadcast Single Frequency Network).
The SC-FDMA is a transmission scheme where a frequency band is divided and the different frequency bands are utilized for multiple terminals for reduction in interference among the terminals. Since the SC-FDMA has characteristics of reduced variations of transmission power, it can reduce power consumption in the terminals and realize broader coverage.
The SC-FDMA used for uplink radio access in E-UTRA is described with reference to FIG. 1. The frequency band usable in the system is divided into multiple resource blocks, each resource block including one or more subcarriers. The user apparatus (UE: User Equipment) is assigned one or more resource blocks. In the frequency scheduling, a resource block is preferentially assigned to a user apparatus in good channel state according to received signal quality or channel state information (CQI: Channel Quality Indicator) for each uplink resource block of each user apparatus measured by the base station apparatus, so that transmission efficiency or throughput of the whole system can be improved. Also, frequency hopping may be applied where usable frequency blocks are changed according to a predetermined frequency hopping pattern.
In FIG. 1, different hatching patterns indicate time/frequency resources assigned to different user apparatuses respectively. Although UE2 is assigned a wide band, it is assigned a narrow band in a next subframe. Different frequency bands are assigned to user apparatuses respectively such that the frequency bands do not overlap with each other.
In the SC-FDMA, each user apparatus in a cell performs transmission using different time/frequency resources. Accordingly, orthogonalization between user apparatuses in the cell is realized. In the SC-FDMA, by assigning continuous frequencies, single-carrier transmission of low PAPR (Peak-to-Average Power ratio) can be realized. Therefore, coverage area can be widened in the uplink where limitation for transmission power is strict. In the SC-FDMA, a scheduler of the base station apparatus determines the time/frequency resource to be assigned based on propagation state of each user, and QoS (Quality of Service) of data to be transmitted. Here, QoS includes a data rate, a required error rate, and delay. As mentioned above, by assigning time/frequency resources of good propagation state to each user, throughput can be increased.